The invention relates to cardiac pacemakers in general, and more particularly to improvements in devices (hereinafter called fittings) which are used to connect implanted or implantable leads with cardiac pacemakers.
Fittings which serve to connect the conductor of an implanted or implantable lead with a cardiac pacemaker normally comprise a terminal (hereinafter called socket) which is connectable with the proximal end of the conductor of the lead and can be plugged into the pacemaker. The socket is normally hollow to receive the proximal end of the conductor, and the socket is coupled with an insulating sleeve which can be coupled to the insulating tube of the lead. The means for electrically connecting the socket with the proximal end of the conductor normally comprises one or more screws which mesh with and extend radially of the socket. The tips of the screws can be driven into the socket to engage the confined proximal end of the conductor. The screw or screws are rotatably mounted in a tubular extension of the socket. A drawback of such proposals is that the space requirements of the socket and of its screw or screws (as seen in the radial direction of the socket) are excessive, i.e., such sockets cannot be plugged into modern pacemakers which have relatively small inlet openings for the sockets.
Commonly owned published German patent application No. 33 04 506 discloses a fitting wherein the socket has an extension for a hollow cylindrical member consisting of convoluted wire and serving to receive the proximal end of the conductor. The hollow cylinder can be deformed into engagement with inserted proximal end of the conductor by a radially disposed screw which is rotatably mounted in the extension of the socket. An advantage of the proposal which is disclosed in the published German patent application is that the proximal end of the conductor is not directly engaged by one or more screws; however, the space requirements of this fitting (in the radial direction of the socket) are still excessive for use with the latest models of pacemakers. Pursuant to international agreements, the diameters of inlet openings of modern cardiac pacemakers are much smaller than in older pacemakers. The diameters should not exceed approximately 3.2 mm which excludes the aforediscussed conventional fittings from use in conjunction with modern pacemakers. On the other hand, it is desirable that a patient who is in need of a new pacemaker receive a modern pacemaker and that such modern pacemaker be connectable with the conductor of an implanted lead.
U.S. Pat. No. 3,880,169 to Starr et al discloses a fitting wherein the part which is connectable to the pacemaker is a pin having an axial blind bore for the proximal end of the conductor. The material surrounding the blind bore is crimped into engagement with the proximal end of the conductor and the latter is further surrounded by a protective wire coil which is introduced into the proximal end of insulating tube of the lead. A standard bayonet mount surrounds the pin and serves to connect the latter with a cardiac pacemaker. The space requirements of this patented fitting are greater than those of the fitting which is disclosed in the commonly owned German patent application No. 33 04 506.
Commonly owned published European patent application No. 0 219 608 discloses an intravenously implantable lead with an electrode provided at the distal end of the conductor and having an external thread for reliable anchoring in the heart. A sleeve is employed to guide the lead during introduction into the vein and such sleeve can be peeled off the introduced lead by destroying its longitudinally extending weakened zones.
Published German patent application No. 30 35 531 of O'Neill discloses a fitting wherein the smaller-diameter distal end of a connecting pin extends into the proximal end of the conductor. The proximal end of the conductor is surrounded by a crimped sleeve which, in turn, is surrounded by the insulating tube of the lead. The insulating tube is surrounded by a bulky connecting sleeve of silicone rubber.